In recent years and continuing, with the development of digital technology and data compression technology, optical disks such as the CD (compact disk) and the DVD (digital versatile disk) are commonly being applied as media for recording information such as music, photographs, and computer software, for example (referred to as ‘contents’). Also, with the decrease in price of such optical disks, optical disk apparatuses configured to record information on such optical disks are becoming increasingly popular.
An optical disk apparatus may be configured to record/erase information on/from an optical disk having a spiral track or concentric tracks formed thereon by irradiating a laser beam emitted from a light source and forming microscopic spots on a recording layer of the optical disk. The optical disk apparatus may also be configured to reproduce information based on light reflected from the recording layer. The optical disk apparatus may include an objective lens, an optical system for guiding a light flux irradiated from the light source to the recording layer and guiding a reflected light flux that is reflected from the recording layer to a predetermined light receiving position, and an optical pickup device including an optical detector that is disposed at the light receiving position, for example.
Information may be recorded on an optical disk based on the lengths of mark/space areas having differing reflection rates and combinations thereof. Upon recording information on an optical disk using an optical disk apparatus, the light emitting power of the light source of the optical disk apparatus is controlled to enable a mark area and a space area to be formed at predetermined positions on a recording layer of the optical disk.
For example, in the case of recording information on a rewritable optical disk such as the CD-RW (CD-rewritable), the DVD-RW (DVD-rewritable), or the DVD+RW (DVD+rewritable) that includes special alloy in the recording layer as recording material, a mark area is formed by creating an amorphous state through heating the special alloy to a first temperature and rapidly cooling the special alloy thereafter. On the other hand, a space area is formed by creating a crystallized state through heating the special alloy to a second temperature (<first temperature) and gradually cooling the special alloy thereafter. In this way, the mark area is arranged to have a reflectance rate that is lower than that of the space area. The temperature control of the special alloy as is described above may be realized by controlling the light emitting power of the light source. Upon creating the mark area, the light emitting power may be arranged into plural pulses in order to hinder influences from heat accumulation. Such a method of controlling the light emitting power is referred to as the multi-pulse recording method. Also, the maximum value of the multi-pulse light emitting power is referred to as the recording power, and the minimum value of the multi-pulse light emitting power is referred to as the bias power. Also, the light emitting power for creating the space area is referred to as the erasing power (recording power>erasing power>bias power).
In the optical disk apparatus, before recording information on an optical disk, test writing is performed on a predetermined test writing area, referred to as PCA (Power Calibration Area), to obtain the optimum recording power so that a mark and a space may be formed on the optical disk at desired positions with desired lengths (e.g., see Japanese Patent No. 3259642, Japanese Patent No. 3124721, and Japanese Laid-Open Patent Publication No. 2005-190643). Such a process is referred to as an OPC (Optimum Power Control) process.
It is noted that in recent years and continuing, the amount of contents being recorded on an optical disk is increasing, and in turn, there is a growing demand for an optical disk with increased recording capacity. In this respect, an optical disk that is arranged to have light irradiated thereon from one side and includes plural recording layers is being developed (referred to as ‘single-sided multilayer optical disk’ hereinafter) as one way of increasing the recording capacity of the optical disk, and an optical disk apparatus configured to perform processes on such a single-sided multilayer optical disk is also being developed.
It is noted that in the single-sided multilayer optical disk, the light emitting power has to be controlled with greater accuracy. With the growing demand for higher recording speed, it is expected that a recording operation capable of stably recording information on a single-sided multilayer optical disk with good recording quality may not be realized based on the optimum recording power obtained through conventional power determining methods such as those disclosed in Japanese Patent No. 3259642, Japanese Patent No. 3124721, or Japanese Laid-Open Patent Publication No. 2005-190643, for example.